[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Norman Petry and I (Ossipoff) recommended CSSD, but Schwartz Woodall is a better voting system for Debian

On Wed, May 08, 2013 at 10:28:26AM -0400, Michael Ossipoff wrote:
> Below, I'll show examples of what can happen, but first I'll just
> verbally summarize what can happen: First of all, of course A is the
> CW. A is the "sincere CW". In comparison to each of the other
> candidates, more people prefer A to the other candidate than
> vice-versa. A should win, and would win in CSSD, or any Condorcet
> method, under sincere voting.

So my understanding of things is that for your first 2 examples,
voters for B being dishonest resulted in C winning, so they really
failed in what they were trying to do.  They would have been
happier if they didn't try to game the vote.

In the 3rd example A still seems te be winner, so they again
failed in their attempt to game the vote, but we now still have
the winner that we wanted.

So either our system doesn't work like you think it does, or you
need to fix your examples.

> In the example-tables below, the number on the left,on each line, is
> the number of voters who have the preferences stated on that line, or
> who vote the rankings stated on that line.  "A>B>C" indicates
> preference for A over B, and for B over C.  ...or a ranking of A over
> B, and B over C. ">>" indicates a much stronger preference.

Note that we always have a default option too, let's call that D.
This can be used to indicate if you think an option is acceptable
or not, and the majority of the voters need to say they find that
option acceptable or not.  I'm going to assume that with the ">>"
you mean that the other option is not acceptable.

> I'll give 3 examples.
> Example 1:
> Sincere preferences:
> 99: A>B>>C
> 2: B>A>>C
> 100: C>>(A=B)

With option D added, this would be:
99: A>B>D>C
2: B>A>D>C
100: C>D>(A=B)

> The A voters rank sincerely, and the B voters defect:
> 99: A>B
> 2: B
> 3: C

So they vote:
99: A>B>D>C
2: B>D>(A=C)
99: C>D>(A=B)

But if you then look at the result, assuming a simple 1:1 majority
requirement, you see that:
A>D: 99, D>A: 101, A is dropped because it didn't reach majority
B>D: 101, D>B: 99, B is kept
C>D: 99, D>C: 101: C is dropped

So suddenly B wins, because it's the only one that reaches
majority requirements.

> 2 defecting B voters have stolen the election from 99 co-operative A voters.
> ----------------------------
> Here's another example in which the 3 factions are nearly equal in size:
> Sincere preferences:
> 33: A>B>>C
> 32: B>A>>C
> 34: C>>(A=B)

33: A>B>D>C
32: B>A>D>C
34: C>D>(A=B)

> Actual votes, when A voters co-operate and B voters defect:
> 33: A>B
> 32: B
> 34: C

33: A>B>D>C
32: B>D>(A=C)
34: C>D>(A=B)

A>D: 33, D>A: 66, A is dropped
B>D: 65, D>B: 34, B is kept
C>D: 34, D>C: 65, C is dropped

B is the winner again

> Sincere preferences:
> 26: A>B>>C
> 25: B>A>>C
> 49: C>>(A=B)
> Actual rankings, when the A voters rank sincerely and the B voters defect:
> 26: A>B
> 25: B
> 49: C

26: A>B>D>C
25: B>D>(A=C)
49: C>D>(A=B)

A>D: 26, D>A: 74, A is dropped
B>D: 51, D>B: 49: B is kept
C>D: 49, D<C: 51: C is dropped

B is again the winner

So their clearly is a problem because of the majority requirement,
and by marking something not acceptable even when it is, it could
results in an other option winning that what should have won.

Can you make your suggestions again, taking the above into


Reply to: